1. Field of the Invention
The invention relates to a transportable lamp consisting of at least one lighting means which is received in a holding device, and to which voltage is admitted via a cable feed line, whereby an at least partly transparent lamp screen is arranged around the lighting means.
2. The Prior Art
Transportable lamps of said type are known as hand-held or standing lamps and are preferably used for temporarily lighting rooms or outdoor areas. Such lamps may be lamps with a low output or also lamps with up to 1000 watts or more output depending on the intended purpose of application. The more powerful lamps are preferably used outdoors for lighting, for example a construction site, locations where an accident or extensive damage occurred, or at sports events.
A lamp equipped with a balloon is known, for example from European patent application EP 0 834 693, in connection with which the balloon screen or shade is used for diffused scattering of the light, and an excess pressure is generated within the balloon shade by a compressor arranged on the inside. The balloon screen is initially tensioned due the excess pressure and the pressure in the balloon is measured by means of suitable pressure sensors. With adequate inside pressure, the lighting means is switched on or off via a safety circuit. It was found in the operation of such a lamp that the balloon screen can get very easily damaged depending on for which purpose the lamp is used, with cracks or holes being caused, for example by metal chips flying about in the construction industry, or by glowing ashes in fire fighting operations. Smaller holes or cracks in the textile balloon shade will not have any influence on the lighting; however, the pressure loss leads to premature shutoff of the lamp by the pressure difference sensor. Even smaller cracks and scores in the diffusion screen caused by regular packing, set-up and dismounting of the portable lamp lead to the fact that the final pressure required for switching on the lamp is no longer reached. The compressor arranged within the balloon screen is in fact capable of compensating a minor loss of pressure; however, the safety difference pressure switch leads to untimely shutoff of the lamp, as a rule. Such lamps, therefore, can be used only conditionally or not at all in certain work areas.